Sharifa Zaithun Begum, Emilia AbdulMalek, Mohamed Ibrahim Mohamed Tahir, Karen Anne Crouse, Mohd Basyaruddin Abdul Rahman
Integrated Chemical BioPhysics Research, Faculty of Science, Universiti Putra Malaysia 43400 UPM Serdang Selangor Malaysia.
Department of Chemistry, Faculty of Science, Universiti Putra Malaysia 43400 UPM Serdang Selangor Malaysia
RSC Adv. 2018 Oct 2;8(59):34004-34011. doi: 10.1039/c8ra06814c. eCollection 2018 Sep 28.
Copper(ii)-peptides are widely used as industrial catalysts such as in the aerobic oxidation of organic molecules, formation of new C-H bonds and in the azide-alkyne cycloaddition reaction. The length of peptides and the effect of adding copper metal into peptides were questioned in their field of applications. Five novel histidine-based tetrapeptides with the sequences HAAD (P1), HAFD (P2), HAVD (P3), AGHD (P4) and PGHD (P5) were synthesized using the solid phase peptide scheme and analysed with high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) with percentage purities as high as 99.5%. All the peptides were positively charged (+1) and the molecular weight calculated from / values of MS results coincided with the theoretical molecular weight of the peptides. Copper(ii)-peptides derived from these peptides and copper(ii) acetate monohydrate (CuP1-CuP5) in a 1 : 2 ratio was synthesised, purified and characterised by ultraviolet-visible spectroscopy (UV-Vis), ultraviolet-fluorescence spectroscopy (fluorescence) and fourier transform infrared spectroscopy (FTIR), circular dichroism spectroscopy (CD) and optical rotation polarimetry. It provided the necessary information on the secondary structure and the successful binding of copper(ii) to the specific amino acids, hence leading to the putative geometry of copper(ii)-peptides and the difference in the chirality of amino acids, peptides and copper(ii)-peptides. The catalytic activities of the synthesised complexes were evaluated. CuP1 & CuP3 catalysed both the asymmetric aldol reactions with high enantioselectivity of -nitrobenzaldehyde with cyclohexanone (% ee = 87.3 & 80.3, respectively) and of -anisaldehyde with cyclohexanone (% ee = 95.5 & 90.9, respectively).
铜（II）-肽被广泛用作工业催化剂，例如用于有机分子的有氧氧化、新C-H键的形成以及叠氮化物-炔烃环加成反应。肽的长度以及向肽中添加铜金属的效果在其应用领域受到质疑。使用固相肽合成方案合成了五种具有HAAD（P1）、HAFD（P2）、HAVD（P3）、AGHD（P4）和PGHD（P5）序列的新型组氨酸基四肽，并通过高效液相色谱（HPLC）和液相色谱-质谱联用（LC-MS）进行分析，纯度高达99.5%。所有肽均带正电荷（+1），由MS结果的/值计算出的分子量与肽的理论分子量相符。以1∶2的比例合成、纯化并通过紫外可见光谱（UV-Vis）、紫外荧光光谱（荧光）、傅里叶变换红外光谱（FTIR）、圆二色光谱（CD）和旋光偏振法对由这些肽和一水合醋酸铜（II）衍生的铜（II）-肽（CuP1-CuP5）进行了表征。它提供了有关二级结构以及铜（II）与特定氨基酸成功结合的必要信息，从而得出铜（II）-肽的假定几何形状以及氨基酸、肽和铜（II）-肽在手性方面的差异。对合成的配合物的催化活性进行了评估。CuP1和CuP3均催化了与环己酮的不对称羟醛反应，对硝基苯甲醛的对映选择性较高（分别为%ee = 87.3和80.3），以及与环己酮的对甲氧基苯甲醛的对映选择性较高（分别为%ee = 95.5和90.9）。
